Molecular Dynamics Simulation Of Antifreeze Protein Ice-Water Composite System

Antifreeze proteins(AFPs)are a diverse class of proteins that have been identified from a variety of sources,including fish,insects,bacteria,plants,and fungi that living in low temperature environment.Antifreeze protein can adsorb on surface of ice crystals to inhibit the growth and recrystallization of ice crystals.The depression of the growth point of ice crystal is a non-colligative manner.The difference between ice crystal growth point and melting point temperature is called thermal hysteresis.Because the special properties of antifreeze proteins,they are widely used in food storage,biomedical,natural gas transportation and so on.In this paper,the dynamic properties of four proteins(Choristoneura fumiferana antifreeze protein(CfAFP),Zoorces americanus antifreeze protein(ZaAFP)and non-antifreeze protein Viscum album toxin protein,homo sapiens Vimentin in low temperature aqueous solution were analyzed by used the whole atomic molecular dynamics simulation(MD)method.The simulation results show that structures ofCfAFP,ZaAFP and Viscum album toxin protein are stable in low temperature aqueous solution,while the structure of homo sapiens Vimentin is unstable.And homo sapiens Vimentin can not keep biology activity when the structure is incompact.Then,the effects of adsorbed proteins on the structure of ice-water interface system at the basal plane and prism face were analyzed respectively.The results show that solid state water molecules in the ice-water interface layer are more likely to translate into liquid state water molecules with CfAFP and ZaAFP adsorbed on the surface of ice crystals.But the non-antifreeze protein has no significant effects.Finally,the hydrophobicity of amino acid sequences of the three kinds of protein were analyzed.It was found that hydrophobicity of antifreeze proteins CfAFP and ZaAFP are more powerful than hydrophobicity of the non-antifreeze protein.Liquid phase water molecules that close to ice-joint surface of antifreeze proteins are inclined to form an ice-like structure.And the progress of liquid phase water molecules translate into solid state in interface layer can be disturbed by ice-like structure near antifreeze proteins.The above simulation results provide a new idea for explaining the mechanism of antifreeze protein thermal hysteresis activity at the molecular level.